title: Phosphorylation of BLUS1 kinase by phototropins is a primary step in stomatal opening.
abstract: Opening of stomata in the plant facilitates photosynthetic CO2 fixation and transpiration. Blue-light perception by phototropins (phot1, phot2) activates the plasma membrane H(+)-ATPase, causing stomata to open. Here we describe a regulator that connects these components, a Ser/Thr protein kinase, BLUS1 (BLUE LIGHT SIGNALING1), which mediates a primary step for phototropin signalling in guard cells. blus1 mutants identified by infrared thermography result in a loss of blue light-dependent stomatal opening. BLUS1 encodes a protein kinase that is directly phosphorylated by phot1 in vitro and in vivo at Ser-348 within its C-terminus. Both phosphorylation of Ser-348 and BLUS1 kinase activity are essential for activation of the H(+)-ATPase. blus1 mutants show lower stomatal conductance and CO2 assimilation than wild-type plants under decreased ambient CO2. Together, our analyses demonstrate that BLUS1 functions as a phototropin substrate and primary regulator of stomatal control to enhance photosynthetic CO2 assimilation under natural light conditions.
authors.affiliation: Department of Biology, Faculty of Science, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takemiya
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Sugiyama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fujimoto
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Tsutsumi
authors.forename: Shota
authors.initials: S
authors.lastname: Yamauchi
authors.forename: Asami
authors.initials: A
authors.lastname: Hiyama
authors.forename: Yasuomi
authors.initials: Y
authors.lastname: Tada
authors.forename: John M
authors.initials: JM
authors.lastname: Christie
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Shimazaki
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D057486:Carbon Cycle / Q000187:drug effects / Q000528:radiation effects; D002245:Carbon Dioxide / Q000494:pharmacology; D003001:Cloning, Molecular; D017343:Genes, Plant / Q000235:genetics; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D010768:Phosphoserine / Q000378:metabolism; D056949:Phototropins / Q000378:metabolism*; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D013696:Temperature
chemical_list: D029681:Arabidopsis Proteins; D056949:Phototropins; D002245:Carbon Dioxide; D010768:Phosphoserine